1. Field of the Invention
This invention relates to a chain pin made of synthetic resin used for connecting chain links, and to a chain made of synthetic resin including such pins.
2. Description of the Prior Art
It has been usual to use a pin having a flange at one end for connecting adjoining links in a metal chain, such as of steel or cast iron, and to retain the pin in position by fitting a split or J-shaped pin at another end of the pin, or by upsetting another end of the pin. A chain of synthetic resin has, however, come to be often used in sewer systems, etc., and the methods employed for retaining pins in a metal chain as described above are not applicable to such a chain of synthetic resin.
Japanese Utility Model Publication No. 61-12440 discloses a chain pin which is made of synthetic resin and is still suitable for connecting chain links. The pin has a central cylindrical cavity and a forward cylindrical cavity, the latter being formed at the forward end portion of the pin, forming an extension of the central cavity, and defining the interior of an annular shell. The shell has a shoulder of enlarged diameter and is cut by axial slots to define flexible tangs. When the pin is inserted into the aligned bores of links, the annular shell is elastically deformed to a smaller diameter for insertion of the pin. After the pin passes through the bores of the links, the shoulder restores its original diameter to engage with the outer link, thereby retaining the pin in position.
However, the annular shell has a small wall thickness which creates a problem when the pin is to be removed from the links, though it does not present any problem when the pin is going to be inserted into the links. Its small wall thickness does not allow the shell to be struck with a hammer, or the like, but calls for the use of a special tool for the removal of the pin. Moreover, the central cylindrical cavity of the pin lowers its shearing and bending strength.